1. Field of the Invention
Embodiments of the invention relate to a stereoscopic image display and a method for driving the same capable of implementing a two-dimensional plane image (hereinafter referred to as “2D image”) and a three-dimensional stereoscopic image (hereinafter referred to as “3D image”).
2. Discussion of the Related Art
A stereoscopic image display implements a 3D image using a stereoscopic technique or an autostereoscopic technique.
The stereoscopic technique, which uses a parallax image between user's left and right eyes with a high stereoscopic effect, may include a glasses type method and a non-glasses type method. In the glasses type method, the parallax image between the left and right eyes is displayed on a direct-view display or a projector through a change in a polarization direction of the left and right parallax image or in a time-division manner, and thus a stereoscopic image is implemented using polarization glasses or liquid crystal shutter glasses. In the non-glasses type method, an optical part such as a parallax barrier and a lenticular lens for separating an optical axis of the left and right parallax image is generally installed in front of or behind a display screen, and thus the stereoscopic image is implemented.
FIG. 1 illustrates a related art glasses type stereoscopic image display. As shown in FIG. 1, the glasses type stereoscopic image display implements a stereoscopic image using polarization characteristic of a patterned retarder 5 disposed on a display panel 3 and polarization characteristic of polarization glasses 6 the user wears. The display panel 3 separately assigns a left eye image L and a right eye image R to adjacent display lines and displays the left and right images L and R. The patterned retarder 5 varies polarization characteristic of the left eye image L and polarization characteristic of the right eye image R differently from each other and separates polarizations of the left eye image L and the right eye image R. A left eye lens of the polarization glasses 6 transmits the polarization of the left eye image L and intercepts the polarization of the right eye image R. A right eye lens of the polarization glasses 6 transmits the polarization of the right eye image R and intercepts the polarization of the left eye image L. In FIG. 1, a reference numeral 1 denotes a backlight unit providing light to the display panel 3, and reference numerals 2 and 4 denote polarizing films respectively attached to an upper substrate and a lower substrate of the display panel 3.
In the glasses type stereoscopic image display shown in FIG. 1, visibility of a 3D image is reduced due to a crosstalk generated at a position of a vertical viewing angle. The user's left eye has to transmit only light of the left eye image L and the user's right eye has to transmit only light of the right eye image R, so as to prevent the crosstalk of the 3D image. However, when both light of the left eye image and light of the right eye image are incident on each of the user's left and right eyes, the user simultaneously sees the light of the left eye image and the light of the right eye image through the user's left or right eye. Namely, the user feels a left/right eye crosstalk. When the users does not watch the 3D image in the front of the display panel 3 and looks down or up the 3D image, each of a left eye patterned retarder 5a and a right eye patterned retarder 5b transmits both the light of the left eye image and the light of the right eye image at a vertical viewing angle, which is greater than a front viewing angle by an angle equal to or greater than a predetermined angle. This may lead to the crosstalk. Thus, the related art glasses type stereoscopic image display shown in FIG. 1 has the very narrow vertical viewing angle at which the 3D image can be displayed without generating the crosstalk.
Thus, as shown in FIG. 2, Japanese Laid Open Publication No. 2002-185983 discloses a method for widening a vertical viewing angle of a stereoscopic image display by forming black stripes BS on a patterned retarder 5. When the user observes the stereoscopic image display at a location spaced apart from the stereoscopic image display by a predetermined distance D, a vertical viewing angle α, at which the crosstalk is not theoretically generated, depends on the size of black matrixes BM of a display panel 3, the size of the black stripes BS of the patterned retarder 5, and a distance S between the display panel 3 and the patterned retarder 5. The vertical viewing angle α widens as the size of the black matrixes BM and the size of the black stripes BS increase and as the distance S between the display panel 3 and the patterned retarder 5 decreases.
The stereoscopic image display shown in FIG. 2 having the black stripes BS on the patterned retarder 5 has the following problems.
First, the black stripes BS on the patterned retarder 5 contribute to an increase in the vertical viewing angle of the stereoscopic image display, but interact the black matrixes BM of the display panel 3 to thereby generate Moire. In this instance, when the stereoscopic image display displays a 2D image, visibility of the 2D image is greatly reduced because of the Moire. Second, a luminance of the 2D image displayed on the stereoscopic image display is greatly reduced because of the black stripes BS of the patterned retarder 5. This is because some of pixels of the display panel 3 are covered by the black stripes BS of the patterned retarder 5.
To solve the problems of the stereoscopic image display disclosed in Japanese Laid Open Publication No. 2002-185983, the present applicant has proposed a stereoscopic image display for dividing each of pixels of a display panel into two parts and using one of the two parts as an active black stripe in U.S. application Ser. No. 12/536,031 (Aug. 5, 2009) which is hereby incorporated by reference in their entirety. The stereoscopic image display disclosed in U.S. application Ser. No. 12/536,031 may prevent a reduction in a luminance of a 2D image by dividing each of the pixels into the two parts and writing 2D image data to each of the divided pixels in a 2D mode. Further, it may improve the visibility of both the 2D and 3D images by widening a vertical viewing angle in a 3D mode. Hence, it may provide more excellent display quality than the existing stereoscopic image display.
The user does not feel a stereoscopic feeling about a portion of data in the related art stereoscopic image display and may feel a noise called an artifact. This may be described by a binocular fusion phenomenon and a binocular rivalry phenomenon. As shown in FIG. 3, the binocular fusion phenomenon is that when visual informations, which are similar to as each other, are incident on each of the user's left and right eyes, a left eye image and a right eye image are fused with each other in the user's brain to generate one independent information fused in the user's brain. Thus, the user may perceive a stereoscopic image with a sufficiently stereoscopic feeling by the binocular fusion phenomenon. On the other hand, as shown in FIG. 4, the binocular rivalry phenomenon is that when different visual informations are incident on each of the user's left and right eyes, the different visual informations are competitively transferred to the user's brain to cause the artifact. If a non-stereoscopic image is divided into a left eye image and a right eye image and is displayed on the stereoscopic image display shown in FIG. 1 using a spatial division method, the user may perceive the artifact, which is completely different from an original image, from the stereoscopic image display shown in FIG. 1 due to the binocular rivalry phenomenon. The non-stereoscopic image is a non-stereoscopic image which has a high spatial frequency and has little a 3D depth between a left eye image and a right eye image of the non-stereoscopic image. As an example of the non-stereoscopic image, as shown in FIG. 12, there is a text image represented in a small space. If the text image shown in FIG. 12 is divided into a left eye image and a right eye image and is displayed on the stereoscopic image display shown in FIG. 1, the binocular rivalry phenomenon is caused because the left eye image and the right eye image are completely different from each other.